This invention relates to personal computers, and particularly to a personal computer having provision for identifying the storage capability of removable media used in a direct access storage device associated with the computer.
Personal computer systems in general and IBM personal computers in particular have attained widespread use for providing computer power to many segments of today's modern society. Personal computer systems can usually be defined as a desk top, floor standing, or portable microcomputer that consists of a system unit having a single system processor and associated volatile and non-volatile memory, a display monitor, a keyboard, one or more diskette drives, a fixed disk storage, and an optional printer. One of the distinguishing characteristics of these systems is the use of a motherboard or system planar to electrically connect these components together. These systems are designed primarily to give independent computing capability to a single user and are inexpensively priced for purchase by individuals or small businesses. Examples of such personal computer systems are IBM's PERSONAL COMPUTER XT and AT and IBM's PERSONAL SYSTEM/2 Models 25, 30, 50, 60, 70 and 80 .
These systems can be classified into two general families. The first family, usually referred to as Family I Models, use a bus architecture exemplified by the IBM PERSONAL COMPUTER XT, AT and other "IBM compatible" machines. The second family, referred to as Family II Models, use IBM's MICRO CHANNEL bus architecture exemplified by IBM's PERSONAL SYSTEM/2 Models 50 through 80. Many Family I models used the popular INTEL 8088 or 8086 microprocessor as the system processor. These processors have the ability to address one megabyte of memory. Certain Family I and most Family II models typically use the high speed INTEL 80286, 80386, and 80486 microprocessors which can operate in a real mode to emulate the slower speed INTEL 8086 microprocessor or a protected mode which extends the addressing range from 1 megabyte to 4 Gigabytes for some models. In essence, the real mode feature of the 80286, 80386, and 80486 processors provide hardware compatibility with software written for the 8086 and 8088 microprocessors.
Such personal computers are characterized as having an "open" architecture. That is, the systems are designed and constructed in such a way that additional peripheral devices, such as removable media direct access storage devices (or DASD) may be selected and added to the systems, or an existing device may be changed for a device of a different type. The floppy disk drives mentioned above are one example of a removable media DASD. By way of example, the original Family I machines were often assembled a with a 5.25 inch, high capacity (or high density) floppy disk drive having the capability of storing 1.2 megabytes of data on a diskette. However, such machines could be equipped with a previously known type of DASD which used a 5.25 inch disk to store 360 kilobytes of data. Family II machines may have DASD using 3.5 inch diskettes to store 780 kilobytes or 1.44 megabytes of data. It is known and contemplated that other removable media DASD may be provided and may be used in or with personal computers of the general types described. Certain difficulties are raised by the fact that removable media used with various types of DASD have the same physical form factor. That is, a 5.25 inch diskette may be formatted to either one of two different storage capabilities, while a 3.5 inch diskette may conceivably be formatted to any of three.
Heretofore, it has been conventional to provide in a personal computer of the type described a central processor unit for executing instructions and manipulating data and a direct access storage device controller operatively interposed between the processor unit and the DASD for controlling the writing of data to and the reading of data from the removable media of the DASD. It has been contemplated that provision may be made in the operation of a personal computer for recognition of the type of DASD used and the storage characteristics of the media inserted into such as drive. The interested reader is referred to Berens et al U.S. Pat. No. 4,733,036 issued Sep. 20, 1988 and Agoglia et al U.S. Pat. No. 4,928,193 (both owned in common with the invention here to be described) for disclosures of apparatus and methods for determining diskette drive and media types. To any extent necessary or appropriate for an understanding of this invention, the disclosures of those prior patents are hereby incorporated by reference into this description.